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9.Straight Line
easy
If vertices of a parallelogram are respectively $(0, 0)$, $(1, 0)$, $(2, 2)$ and $(1, 2)$, then angle between diagonals is
A
$\pi /3$
B
$\pi /2$
C
$3\pi /2$
D
$\pi /4$
Solution
(d)Here,
Slope of Ist diagonal= ${m_1} = \frac{{2 – 0}}{{2 – 0}} = 1$
$\Rightarrow {\theta _1} = {45^o}$
Slope of IInd diagonal= ${m_2} = \frac{{2 – 0}}{{1 – 1}} = \infty $
$\Rightarrow {\theta _2} = {90^o}$
==>${\theta _2} – {\theta _1} = {45^o} = \frac{\pi }{4}$.
Standard 11
Mathematics